In surgical and orthopedic treatments, prosthesis operations are often required for filling in defects or hollow portions of bone which may result from fracture of bone or surgical removal of bone tumor. Also in the field of dental surgery, similar denture operations are often required for filling in spoiled void portions in maxilla or mandible resulting from pyorroea alveolaris. It has been a common practice to harvest bone from donor site, for example from the iliac crest of the patient to fill up the defect or hollow portion of bone and thereby to promote the regeneration of the bone tissue. However, to perform such an operation normal, undamaged bone tissue must be picked up from an unspoiled portion. This operation causes additional pain to the patient and is, in addition, a very troublesome procedure. Moreover, when the volume of the defect or void in the patient's bone is large, the amount of bone obtainable from the patient's own body is not always adequate to fully fill in the defect or void. In such cases it is inevitable to use a substitute for the patient's own bone tissue. Even though the same sort of bone tissue has been used as the substitute, the implanted substitute may be rejected by the living tissue due to the foreign body rejection reaction (by the immune system). For these reasons the post-operation recovery of the defect is not always satisfactory. Accordingly, such an operation has not yet been recognized as fully satisfactory in practice.
There is therefore a demand for an artificial material which has excellent compatibility with living tissues when filled in a defect or hollow portion of bone to facilitate formation of bone within and at the vicinity of the defect and to promote repair and recovery of the structure and function of the once damaged bone tissue.
A variety of metal alloys and organic materials have been used as the substitute for the hard tissues in the living body. However, it has been recognized that these materials tend to dissolve or otherwise deteriorate in the environment of living tissue and that these materials are toxic to the living body and cause so called foreign body rejection reaction. Ceramic materials have been used because of their excellent compatibility with the living body and because they are typically free of the aforementioned difficulties. Artificial bones and teeth have been developed from ceramic materials, particularly alumina, carbon or tricalcium phosphate or from sintered masses or single crystal of hydroxyapatite which have superior compatibility with living body. These embodiments have attracted a good deal of the public attention.
However, the conventional ceramic implant materials have a common disadvantage in that they are inherently too hard and brittle. Therefore these known ceramic materials are not fully satisfactory in practical use. There have been attempts to fill defects in bone with a sintered ceramic block or a ceramic block of single crystal form. However, since uneven gaps or interstices are formed between the block and the bone tissue, the object of fully filling in the void in the bone cannot be attained. On the other hand, when alumina is used as the filler, it acts as a stimulant to cause absorption of bone at the vicinity of the implanted filler due to the fact that alumina is much harder than the bone tissue. Furthermore, it has not been clarified what properties a ceramic material should possess to suppress the foreign body rejection reaction and to improve the compatibility with living body as well as promote formation of new bone.
Heimo Ylänen (Doctoral Thesis, Turku, Finland 2000) has studied bone ingrowth into porous bodies made by sintering bioactive glass microspheres. He has found out that rigid porous bioactive glass implants provide an environment that promotes, throughout the whole implant, an extended incorporation of new bone into space between the sintered bioactive microspheres. As a result the implant is quickly and firmly bonded to the host bone. In the studies it is also noted that the in vitro rate of the reactions inside the porous glass implant is higher than the non-porous glass rods made from the same bioactive glass. The block sintered from bioactive glass spheres is brittle and breaks easily if load is applied to it. Another drawback with blocks sintered from glass spheres is that the porosity is considerably low and this affects bone forming properties in this device.
Publication WO 00/35509 discloses a porous textile product made from bioactive glass and a weakly bioactive glass. Several ways to produce the textile product are suggested in the publication but there is no suggestion of sintering the bioactive glasses together.
Finnish patent 103,715 ('715 patent) discloses a composite made of bioactive material A and of non-bioactive material B or weakly bioactive material B and the materials have been sintered together to a porous composition. According to the '715 patent particles A and B are rounded, preferably spherical. In the '715 patent there is no suggestion to use glass fibers for preparing the composition.
Finnish patent application 923,561 discloses bioactive glass compositions and preparation of implants from the filaments of the said bioactive glass compositions. However, there is no teaching in the publication to sinter the filaments together.
Publication WO 97/31661 describes an osteogenic device which comprises a shapeable porous carrier body selected from hydroxyapatite, tricalcium phosphate, bioactive glass and biocoral. There is no teaching in the publication of using bioactive glass fiber.
U.S. Pat. No. 6,054,400 ('400 patent) discloses an invention which relates to novel bioactive glasses with a large working range and controlled durability. The '400 patent further discloses the use of the bioactive glasses for tissue bonding purposes in the medical or dental field, for use in biotechnology, for controlled release of agents and for tissue guiding. The filling material comprises bioactive glass in crushed form or as spherical granules. There is no suggestion in the US patent to use glass fibers.
U.S. Pat. No. 5,429,996 concerns a bone grafting material for use in medicine which is glass wool having the following composition 40–62% (w/w) SiO2, 10–32% (w/w) Na2O, 10–32% (w/w) CaO, 0–12% (w/w) P2O5, 0–12% (w/w) CaF2, 0–21% (w/w) B2O3. The glass wool has a mean diameter of 100 μm or less. There is no suggestion of using sintered glass fibers in this publication, however.
U.S. Pat. No. 5,468,544 discloses composite materials using bone bioactive glass and ceramic fibers. In more detail in the patent is described composite structures that incorporate a bioactive material in a polymer matrix along with a structural fiber. The polymeric matrix used is a non-bioabsorbable polymeric matrix, for example polysulphone, PEEK or PEKK and the structural fiber is a carbon fiber.
U.S. Pat. No. 4,735,857 describes a fiber glass for filling in a defect or hollow portion of bone. The fiber glass comprises calcium phosphate as a main ingredient and has a negative zeta potential. The fiber glass is of long filament form or staple fiber form and the long filament form may be woven to form a woven filler, for example a cloth or gauze. In the US patent there is no suggestion of sintering the fibers.
U.S. Pat. No. 5,914,356 describes a woven filler for filling in a defect or hollow portion of bone. The woven filler is prepared by weaving fiber glass filaments which fiber glass consists essentially of calcium phosphate and has a negative zeta point as well, and of an inorganic oxide. The inorganic oxide can be alumina, silica, sodium oxide, iron oxide, magnesium oxide, kaolin or a mixture thereof. There is no teaching of sintering the glass fibers in this patent.
U.S. Pat. No. 5,711,960 describes an implant material which comprises as a base material a biocompatible bulk structure of a tri-axial or more three-dimensionally woven fabric of organic fibers, a tri-axial or more three-dimensionally knitted fabric of organic fibers or combination thereof.
U.S. Pat. No. 4,904,257 discloses a method of filling a void in a bond which comprises filling the void with a fibrous bone comprising fibers containing intact hydroxylapatite, water-soluble binder and water.
M. A. De Diego et al. (Tensile Properties of Bioactive Fibers for Tissue Engineering Applications, Journal of Biomedical Materials Research, 2000, Vol. 3,199–203) have studied tensile properties of bioactive fibers for tissue engineering applications. The tested material was 45S5 Bioglasse which is a 4-component, melt-derived bioactive glass. In the study tensile strength, elongation to fracture and Weibull's moduli of 45S5 Bioglasse is reported.
It is also known in the art that the fabrication of 3D scaffolds for skeletal reconstruction from bioceramics and biopolymers has been studied.